During the 13th Probiotics, Prebiotics and New Foods Congress, Microbiomepost.com conducted an exclusive interview with Douwe Van Sinderen, professor of Molecular Microbiology at School of Microbiology & APC Microbiome Ireland.

Bacteriophages—viruses that infect bacteria—represent a largely underestimated challenge in the manufacturing of fermented foods and probiotic products, particularly when lactic acid bacteria are grown in milk-based matrices. In natural ecosystems, phage–bacteria interactions are highly dynamic, with an estimated 50% of all bacteria being lysed daily as a consequence of viral infection. In industrial settings, however, such infections can severely compromise large-scale production of cheese, yogurt and probiotic preparations by destroying starter or probiotic cultures.

This interview focused on bacteriophages infecting lactic acid bacteria used in food and probiotic applications, addressing three main questions: what these phages are, what they have in common, and how they recognize their specific bacterial hosts. Like many viruses, bacteriophages display a narrow host range, and their ability to discriminate between closely related bacterial strains depends on precise recognition mechanisms. In the case of lactic acid bacteria, current evidence indicates that extracellular polysaccharides act as key receptors, providing the molecular structures that phages bind to in order to attach to, and infect, their preferred hosts.

The second part of the interview explored practical strategies to mitigate phage-related problems. A central concept is the mobilization and exploitation of the inherent immune and defense systems that bacteria have evolved over millions of years of co-existence with viruses. By identifying these naturally occurring anti-phage systems and introducing them into selected industrial or probiotic strains, it is possible to enhance the robustness of starter and probiotic cultures. Such approaches offer a promising route to safeguard the continuous supply of high-quality dairy and probiotic products and to secure the future use of these beneficial bacteria for human health.